1. Field of the Invention
The present invention relates to a power transmission apparatus suitable for use in automotive vehicles.
2. Description of the Prior Art
A front-drive (FF) base four-wheel-drive (4WD) vehicle is disclosed in Japanese Published Unexamined (Kokai) Patent Appli. No. 60-172764, for instance, in which a viscous coupling clutch and a clutch device are both arranged on the propeller shaft. In the case where engine power is intermittently transmitted to the wheels via a relatively long propeller shaft rotating at a high rotative speed, since the inertial moment is large and therefore vibration is easily produced, there exists a problem in that the propeller shaft must be supported by special support members when a power transmission is mounted in connection with the propeller shaft.
Further, a vehicle in which a viscous coupling is provided for a transfer of a 4WD vehicle is disclosed in Japanese Published Unexamined (Kokai) Patent Appli. No. 63-13823. In this case, although it is possible to solve the afore-mentioned vibration problem, since the viscous coupling is constructed separately from a differential gear, there exists another problem in that the propeller shaft supporting structure is rather complicated.